fix: CIワークフローのコード生成コマンドを修正

- build_runnerの実行コマンドをdartからflutterに変更し、正しい環境でのコード生成を実施

Author: LibraryLibrarian

.github/workflows/ci.yaml

@@ -68,7 +68,12 @@ jobs:
       - name: Codegen verify (only latest)
         if: matrix.flutter == '3.32.x'
         run: |
-          dart run build_runner build -d --build-filter="lib/**"
+          set -e
+          export FLUTTER_FRONTEND_SERVER_SNAPSHOT="$FLUTTER_ROOT/bin/cache/artifacts/engine/linux-x64/frontend_server.dart.snapshot"
+          echo "Using frontend_server: $FLUTTER_FRONTEND_SERVER_SNAPSHOT"
+          test -f "$FLUTTER_FRONTEND_SERVER_SNAPSHOT" || (echo 'frontend_server snapshot not found' && ls -R "$FLUTTER_ROOT/bin/cache/artifacts/engine" && exit 1)
+          flutter pub get
+          flutter pub run build_runner build -d --build-filter="lib/**"
           git diff --exit-code || (echo 'Codegen produced changes. Please commit generated files.' && exit 1)
 
   example-android: